1. Field of the Invention
The present invention relates to a liquid crystal display device and a manufacturing method therefor.
2. Description of the Related Art
In an active matrix liquid crystal display device, a semiconductor layer and a metal layer are laminated so as to form a thin-film transistor. In a bottom-gate thin-film transistor, a drain electrode, a source electrode, and a drain wiring (wiring which is supplied with a video signal for driving a pixel electrode), which are patterned from the metal layer, are formed on the semiconductor layer. In such a structure, in some cases, the semiconductor layer is used to reduce a difference in level in, for example, a region where the drain wiring overlaps a wiring intersecting therewith, such as a source wiring (WO 01/018597).
Further, in recent years, resolution in display region has been improved. Accordingly, there is a case where two drain wirings are formed for a single pixel (JP 2005-77424 A).
In a method in which the metal layer, which becomes the drain electrode, the source electrode, and the drain wiring to be connected to the drain electrode, is patterned after the semiconductor layer is patterned, considering misalignment, the semiconductor layer is formed larger in width than the metal layer overlapping the semiconductor layer. Therefore, the semiconductor layer under the drain wiring is formed to extend off the drain wiring particularly in a region where the semiconductor layer overlaps another wiring intersecting therewith.
Further, in a method in which the metal layer is laminated on the semiconductor layer, and the metal layer and the semiconductor layer are continuously patterned using a single etching resist, the metal layer becomes smaller than the etching resist due to side etching during wet etching, and hence the semiconductor layer under the drain wiring extends off the drain wiring.
In the case where two drain wirings are formed for a single pixel as described in JP 2005-77424 A, there is a possibility that the extending semiconductor layers which are formed under the adjacent drain wirings, respectively, are brought into contact with each other. This may cause electrical short circuit. In order to avoid this situation, it is conceivable to widen a gap between the drain wirings. In this case, however, because light scattering occurs on the drain wiring, a black matrix which is larger in width than the drain wiring is required. Moreover, when the gap between the drain wirings is widened, an aperture ratio inevitably decreases.